Flappy Bird - Phaser.JS

const PIPES = 8;
const mainState = {
    preload: function () {
        game.load.image('bird', 'assets/bird.png');
        game.load.image('pipe', 'assets/pipe.png');
        game.load.audio('jump', 'assets/jump.wav');
    },
    create: function () {
        this.jumpSound = game.add.audio('jump');
        this.score = 0;
        this.pipes = game.add.group();

        game.stage.backgroundColor = '#71c5cf';
        this.bird = game.add.sprite(100, 245, 'bird');
        this.bird.anchor.setTo(-0.2, 0.5);

        game.physics.startSystem(game.physics.arcade);
        game.physics.arcade.enable(this.bird);
        this.bird.body.gravity.y = 1000;

        const spaceKey = game.input.keyboard.addKey(Phaser.Keyboard.SPACEBAR);
        spaceKey.onDown.add(this.jump, this);

        this.timer = game.time.events.loop(1500, this.addPipes, this);
        this.labelScore = game.add.text(20, 20, "0", {
            font: "30px Arial",
            fill: "#ffffff"
        });
    },
    update: function () {
        if (this.bird.y < 0 || this.bird.y > 490) {
            this.restartGame();
        }
        game.physics.arcade.overlap(this.bird, this.pipes, this.hitPipe, null, this);
        if (this.bird.angle < 20) {
            this.bird.angle += 1;
        }
    },
    jump: function () {
        if (!this.bird.alive) {
            return;
        }
        this.bird.body.velocity.y = -350;
        const animation = game.add.tween(this.bird);
        animation.to({angle: -20}, 100);
        animation.start();
        this.jumpSound.play();
    },
    restartGame: function () {
        game.state.start('main');
    },
    addPipe: function (x, y) {
        const pipe = game.add.sprite(x, y, 'pipe');

        this.pipes.add(pipe);
        game.physics.arcade.enable(pipe);
        pipe.body.velocity.x = -200;

        pipe.checkWorldBounds = true;
        pipe.outOfBoundsKill = true;
    },
    addPipes: function () {
        const holeIndex = Math.floor(Math.random() * 5) + 1;
        for (let i = 0; i < PIPES; i++) {
            if (i !== holeIndex && i !== holeIndex + 1) {
                this.addPipe(400, i * 60 + 10);
            }
        }
        this.score += 1;
        this.labelScore.text = this.score;
    },
    hitPipe: function () {
        if (!this.bird.alive) {
            return;
        }
        this.bird.alive = false;
        game.time.events.remove(this.timer);
        this.pipes.forEach(function(pipe) {
            pipe.body.velocity.x = 0;
        }, this);
    }
};
const game = new Phaser.Game(400, 490);
game.state.add('main', mainState);
game.state.start('main');